Centrifuge devices and methods designed to separate finely divided particulate material from suspending liquid are well known in the art. Such devices and methods have been utilized for the separation of solid blood components from whole blood or from a liquid blood fraction. While the present invention has broader utility than the separation of blood components, for the sake of conciseness the invention will be principally described in terms of the embodiment of separation of solid blood components.
Until relatively recently, blood tranfusions were always given using whole blood. There is, however, growing acceptance within the medical profession for transfusing only those blood components required by a particular patient instead of transfusing whole blood. Transfusing only those blood components necessary preserves the available supply of blood and, in many cases, it is better for the patient. Before blood component transfusions can be widely employed, however, satisfactory blood separation techniques and apparatus must evolve.
One technique which is widely used is plasmapheresis, viz., the separation of whole blood into a plasma rich component and a plasma poor component. Typically, plasmapheresis is employed on a large scale using satellite pouch systems, as described in U.S. Pat. Nos. 3,190,546; 3,211,368 and 3,545,671. Typically, the plasma rich component is retained for later use and the plasma poor component is returned to the donor. Thus, with such systems whole blood is withdrawn from a donor and flows to a pouch containing an anticoagulant. The pouch is then disconnected from the donor phlebotomy line, centrifuged in a swinging bucket type centrifuge in which cells must travel about half the long dimension of the pouch, typically about 12 centimeters. The centrifuge must then be gently slowed to a stop and the pouch carefully lifted from the bucket of the centrifuge while avoiding remixing of the two components. The pouch is mounted in a plasma expressor and supernatant plasma fraction is expressed into a connected plasma pouch, care being given to clamp off the connecting tube between the pouches just before the plasma poor component passes over. The pouch containing the plasma poor component is then reconnected to the phlebotomy line so that the plasma poor component can be returned to the donor.
It often takes approximately 1.5 hours using satellite pouch techniques to obtain 500 milliliters (ml) of separated plasma rich component and to return the plasma poor component to the donor, even though the time for donating a unit of whole blood is only about 20 minutes. This relatively long processing time poses a major limitation on volunteer donor recruitment. Moreover, because the blood pouch is disconnected from the donor at the end of each withdraw cycle and transported to and from a separate centrifuge room for centrifugation there is always a danger of returning blood components to a donor which are not his or her own. As previously mentioned, satellite pouch systems also require careful handling of the separated plasma rich and plasma poor components to avoid remixing, thereby ruining the separation.
In general, devices designed for fractionation and separation of cellular components from whole blood tend to be mechanically complicated, expensive, ineffective and difficult to clean or sterilize for use. For example, U.S. Pat. Nos. 3,096,283; 3,244,362 and 3,297,244 describe a variety of rather mechanically complicated, expensive containers for separating cellular components from whole blood. U.S. Pat. Nos. 4,007,871; 4,010,894; 4,094,461; 4,120,448; and 4,386,730 are directed to centrifuge systems for effecting separation of various fractions of cellular blood components through complicated series of tubing, channels, etc. such that the various separated blood components can be drawn off and recovered.
As can be appreciated, none of the prior art devices provides a totally satisfactory method for removing substantially all cellular components from whole blood inexpensively, quickly, conveniently and in a sterile manner.